The present invention relates to a breathing aid apparatus, in particular for treating people which are prone to the disease called xe2x80x9csleep apnoeaxe2x80x9d.
Sleep apnoea syndrome (SAS) is the accumulation of signs as well as their consequences due to the periodic interruption of respiration during sleep. The re-establishment of respiration generally only occurs when the person concerned wakes up. This phenomenon can occur several hundred times per night, with interruptions of 10 seconds or more each time.
Three types of apnoea syndrome exist, each corresponding to a particular pathology.
The first type, which is the most common, is obstructive apnoea. It results from an obstruction of the upper respiratory tracts caused by a collapse of the tongue and the palate. The respiratory movements continue, but because of this obstruction, air can neither enter nor leave the lungs.
The second type, which is rarer, is called xe2x80x9ccentral apnoeaxe2x80x9d. It is produced when the respiratory center of the brain no longer controls respiration. In the absence of a signal originating from the brain, the respiratory muscles do not function and air can neither enter nor leave the lungs.
The third type is mixed apnoea which is a combination of the two previous types, the start of the apnoea being of central type.
In the case of obstructive apnoea and mixed apnoea, treatment by continuous positive pressure is the most commonly used. This technique consists of permanently applying, via a nasal mask connected by a pipe to a pressure generating apparatus, a low positive relative pressure in the upper respiratory tracts in order to avoid their obstruction. This pressure prevents the tongue and palate from sticking together. The result is immediate: interrupted respiration is re-established, the lungs receive the oxygen they need and the person sleeps much better.
The optimum value of the pressure corresponds to the minimum allowing the suppression of apnoeas and the oxygen desaturations which result in the blood.
Determination of this optimum pressure is carried out in the laboratory, by subjecting the patient to a polygraph recording, and by progressively raising the level of pressure applied to the patient until the disappearance of respiratory incidents.
The treatment described previously, which consists of applying a constant pressure level to the patient throughout the night, has certain deficiencies.
In fact, the frequency and extent of apnoeas vary during the night according to the stage of sleep the patient is in. Also, they vary over time as a function of the development of the condition of the patient (gain or loss of weight, absorption of alcohol before going to sleep . . . ).
Therefore, the treatment pressure determined by the prescription is not necessarily adequate subsequently. Now, control recordings cannot be carried out regularly, due to their cost and the significant burden on sleep laboratories, connected with the large number of patients to be treated.
In addition, the patient is subjected to an identical pressure all night, whereas depending on the stages of his sleep, a lower pressure may be sufficient, or a higher pressure may be necessary. Now, the lower the average pressure applied during the night is, the better the patient""s comfort will be and therefore his acceptance of the treatment, and the more the deleterious effects linked with too high a pressure will be minimised.
The aim of the present invention is to propose a breathing aid apparatus which allows the treatment to be optimized as a function of the effective needs of the patient at each stage of treatment.
According to the invention, the breathing aid apparatus, in particular for treating sleep apnoea, comprising means of producing a flow of breathable gas under a low positive relative pressure, and means for leading this flow to a respiratory mask, is characterized in that in addition the apparatus comprises means of acquiring a parameter representative of the respiratory activity of the patient, and automatic adjustment means for increasing the pressure applied at least when the representative parameter is indicative of a hypopnoea, and for reducing the applied pressure when the representative parameter is indicative of normal respiration over a predetermined time.
The term xe2x80x9chypopnoeaxe2x80x9d encompasses the phenomena of the total disappearance of respiration, and can also include certain phenomena of partial disappearance of respiration, due to a partial obstruction of the upper respiratory tracts.
Thanks to the invention, the treatment apparatus is no longer a simple constant pressure generator, but becomes an apparatus capable of detecting hypopnoeas and of adjusting the pressure level in order to suppress the hypopnoeas.
In this way, thanks to the apparatus, each time a hypopnoea is detected, the pressure is increased, preferably by increments, until the hypopnoea ceases. When no hypopnoea has occurred for a defined period of time, the pressure is reduced by a predetermined value.
This process allows hypopnoeas to be put to an end while permanently minimizing the applied pressure.
Preferably, the pressure cannot go below a lower threshold defined by the consultant and set on the apparatus, and of course it cannot exceed the maximum value that the apparatus is capable of delivering, or a maximum value defined by the doctor.
Other characteristics and advantages of the invention will become apparent from the description below, with reference to the non-limitative examples.